The present invention relates to the measurement of antenna performance parameters in real time. More specifically, but without limitation thereto, the present invention relates to the measurement of voltage, current, resistance, and reactance of a transmitting antenna during normal broadcast.
Previous methods for measuring antenna performance typically required the transmission of a CW signal, which meant interrupting normal communications during the measurement period. The possibility of an undetected malfunction while the transmitter was operating is a factor limiting the confidence in the capability of a communications system.
U.S. Pat. No. 5,233,537 issued on Aug. 3, 1993 and incorporated herein by reference thereto describes a system that solves the problem of testing an antenna while transmitting a frequency shift-keyed signal. FIG. 2 of this patent shows the four components used to measure antenna operating parameters: a sensor to generate a signal representative of antenna feed point voltage and current, a sampling trigger circuit, an A/D converter, and a data processing unit to calculate antenna performance from the sampled voltage and current. Because the antenna parameters change with the frequency of the signal being transmitted, the sampling trigger is required to gate samples to the A/D converter during the time periods when the frequency being measured is transmitted. Separate measurements are performed at each transmission frequency.
A continuing need still exists, however, for an antenna performance monitor that is not dependent on knowledge of the frequency excursions of the transmitted signal.